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enclosure building confusion

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Member - Posts: 38
Member spacespace
Joined: February 24, 2010
Location: Ontario, Canada
Posted: August 12, 2011 at 10:08 AM / IP Logged  
Hey guys so I have some confusion I want to clear up so I can build a custom ported enclosure for my single 12" subwoofer.
First of all I am wondering when you make a vent, does the volume of the vent subtract from the overall enclosure volume?
and my second issue is that when I find port calculators to tune to a certain frequency, it is dependent on the volume of the box to find the length of the port, from what I have read (need to confirm question 1), the volume of the port should be subtracted from teh box volume.
So to tune the port is dependent on its size and the box volume to find the appropriate length, so how exactly is this done if say I use a certain volume BEFORE the port, and onec I add it, the volume WILL decrease due to the port taking up more room. Also how will I know that my tuning is correct since the formula is dependent on volume, but once the port is added, the volume is changed?
Can anyone help me out and help me straighten these issues out?
Thanks a ton, I appreciate any help :)
Silver - Posts: 505
Silver spacespace
Joined: February 23, 2010
Location: United States
Posted: August 13, 2011 at 12:26 AM / IP Logged  

on most older softwares, basically if you are building the box, once you find the box size and port size, add the amount of the port to the box volume before you build the box.

if you already have the box built fishing for port sizes, whatever size you are considering, subtract the port size from the box volume.

it takes a little time but you can end up with more accurate figures.

a few programs ask you if the port will be in or out and do it for you.

some just assume it will be an inny and thats how they work.

other members may  have better advice.

quiet rural missouri, near KC.
If your system moves you physically and not emotionally, you have wasted your money.
toy civic 
Member - Posts: 8
Member spacespace
Joined: October 19, 2011
Location: California, United States
Posted: December 06, 2011 at 9:31 PM / IP Logged  

The answer is you must not include the port volume in your internal volume when calculating for port length and tuning frequency. It is almost like you have two internal volumes to consider.

So your "usable" internal volume + your port volume = your total internal volume.

Hope that makes sense.

Member - Posts: 11
Member spacespace
Joined: September 23, 2013
Location: Massachusetts, United States
Posted: September 25, 2013 at 6:24 AM / IP Logged  
If your having trouble with a ports volume taking away from your internal box's cu. ft. measurements, remember you can also use a braced external port that sticks way out of your enclosure they all work the same way.
Keep on Buggin'

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